The present invention relates to a variable-magnification copying machine incorporating means for automatically varying the magnification.
Conventionally, there are a variety of electronic photocopying machines that perform not only actual-size copying but also provide variable magnification by either reducing or enlarging the size of the draft pictures. When varying the magnification, only standardized sizes of draft and copy papers have been used. For example, to realize either a reduction or an enlargement, copying is normally done using either B4, A4, or B5 size of papers against A3, B4, A4, or B5 size of copy papers. Normally, when either enlarging or reducing the magnification using the same A or B type papers against the same-size draft papers, either a magnification of 140% or 70% has been applied. Likewise, when either enlarging or reducing the magnification from A type to B type or vice versa, about 120% or 80% of the magnification has been applied. A certain prior art has already proposed such a copying machine not only capable of dealing with the standard-size drafts but also capable of performing a variable-magnification copying against papers of any desired size by freely setting a specific magnification against indefinite size of draft papers. When copying such a draft paper having a specific standard size, any of the standardized magnification rates can be applied. Conversely, if the draft paper is of an off-standard size, the operator cannot determine the adequate magnification. For example, when the content of such a draft paper having a size of 180 mm.times.160 mm should be copied against A-4 size papers, the operator cannot easily and correctly determine the applicable enlarging or reducing rate at once. Actually, there were many cases in which the operator inadequately set the magnification rate and wasted many copied papers until the desired magnification was eventually set.
Later, another prior art had also proposed such a technique that first detects the size of the draft paper, followed by computing the magnification needed for the copying in reference to the detected draft size and the mounted copying paper to allow the copying machine to automatically set the computed magnification. This technique permits the copying to be easily done against any desired paper. When using such means for detecting the standard size of the draft paper, a simplified mechanism can be applied. Conversely, such means for detecting the off-standard size of the draft paper in both the horizontal and vertical directions unavoidably involves expensive complexity, and as a result, it has no practical advantage.